1. Field of Invention
The present invention pertaining to diesel, gasoline, alternative-fuel internal combustion engines, is comprised of a closed loop electronic control system, to deliver a more precise amount of oil through a solenoid valve and cooling nozzle to a piston underside, and in particular, shall improve or even optimize the piston dome temperature for the reduction of soot production and particulate matter both in the oil and out the exhaust, allowing for increased engine efficiency at all operating conditions.
2. Description of the Related Art
A typical internal combustion engine includes an engine block with a reciprocating piston within a cylinder bore. The piston assembly travels a fixed distance in a cylinder bore and is connected to a connecting rod which in turn is attached to a rotating crankshaft. The piston is generally comprised of both a dome and a skirt (some cases, not all) and will require oil cooling to the underside of the piston dome for cooling and lubrication purposes. Typical piston cooling on a heavy duty diesel engine is generally accomplished by delivering pressurized oil from the crankcase oil system in the form of a spray or stream through a piston oil nozzle assembly, which is connected to an oil passage generally located inside the lower crankcase area. Moreover, the piston oil nozzle assembly is generally mounted directly in the lower internal crankcase area, adjacent each piston cylinder location.
Present technology for cooling the piston throughout the entire engine operating range, is to supply crankcase oil for cooling through the piston oil nozzle assembly explicitly to satisfy the worst case engine operating condition. Unnecessary high pumping power is required to circulate the engine oil used for cooling. The oil flow is constant for any given engine rpm and not load dependent. Moreover, if the engine is not operated at 100% load condition, resultant excessive cooling to the piston dome underside will result in overcooling the piston dome which contributes to elevated soot levels in the crankcase oil and reduced engine efficiency. To help address this issue, alternative piston cooling management systems have been developed.
For example U.S. Pat. No. 2,800,119 to Schmidl discloses an arrangement for cooling the piston of an internal combustion engine, more particularly, to control the share of lubricating oil branched off to the piston and piston head, in dependence upon engine speed. The improvement comprises a spray nozzle in said piston cooling branch circuit having an opening of a size to permit a flow resistance to the passage of oil less than the flow resistance in the lubricating branch circuit at engine idling speeds. Furthermore, a check valve exits connecting this said nozzle with a means for opening said valve under the pressure of the main oiling circuit during normal engine running speeds, but closing this said valve during low running or engine idling speeds.
While the Schmidl reference discloses a mechanism for cooling the piston throughout a range of engine operating conditions, Schmidl's enhanced spray nozzle introduces a non-return valve and compression spring assembly that will be prone to hysteresis and sticking effects. Furthermore, variations in the oil pumping circuit cannot be compensated by the open loop design of the enhanced spray nozzle, providing a non-optimized solution as thousands of hours of wear are imposed on the cooling system components. In addition, the Schmidl design is regulated by an oil pressure relief valve located in the piston oil nozzle assembly, allowing oil to the piston nozzle until the engine crankcase oil pressure exceeds the predetermined nozzle relief valve setting. At this threshold point, the piston oil spray nozzle starts flowing crankcase oil through the nozzle orifice assembly. The actual oil to the piston cooling nozzle now becomes crudely controlled by the engine rpm, determining the crankcase oil pressure. This simplistic control strategy is typically found in today's modern engines and has a minimal at best opportunity to regulate the desired oil flow to the piston for cooling.
U.S. Pat. No. 5,819,692 issued to Schafer, discloses a control mechanism for spraying lubrication oil to the piston, whereby the temperature of the piston is controlled within a preferable range to prevent overheating under high load conditions, or overcooling at low load conditions. A direct-acting thermostatic valve is positioned into a machined passage in the engine for diverting lubricant from the main oil gallery passage into individual branch passages leading to each spray nozzle.
While the U.S. Pat. No. 5,819,692 reference discloses a method to provide cooling of the piston for a range of engine conditions, the control mechanism relies on a tubular valve element that is reciprocated back and forth in the main oil passage by a thermostatic power element located in the main passage. This valve and thermostatic power element would be difficult to control due to potential sticking and hysteresis effects and would result in a sluggish response rate for the piston cooling methodology. Over the wide spectrum of rpm and load conditions imposed on the piston, mandatory precise cooling needs delivered to the pistons at the required time would be absent.
It is desirable to introduce an electronically controlled solenoid valve actuated by an engine power control module, to regulate oil flow for the purpose of piston cooling. To address this need, U.S. Pat. No. 6,955,142 B2 to Patel discloses the use of an electronic solenoid valve within an oil supply manifold to activate and deactivate an oil squirter system. For low engine rpm, the said solenoid valve would close to restrict oil flow and deactivate the oil squirter. As engine rpm increases, the solenoid valve would open and allow the oil to spray on the pistons and cylinders for lubrication and cooling purposes.
Although the electronically controlled solenoid valve in the Patel patent provides the mechanism for delivering oil for piston cooling, there exists no provision for precisely delivering oil spray based on a plurality of engine load conditions for the purpose of reducing soot production and improving engine efficiency.
Hence, it will be appreciated that there is a continuing need for a robust control methodology to manage the temperature of a piston dome based on rpm and load, by more precisely regulating the flow of crankcase oil.